Method of manufacturing a self-adjusting supporting member having a magnetic head

ABSTRACT

IN HYDRODYNAMICALLY OPERATING SUSPENSION DEVICES WHICH HAVE FOR THEIR OBJECT TO KEEP A MAGNETIC HEAD AT A CONSTANT DISTANCE FROM A ROTATING MEMORY DISK, THE MAGNETIC HEAD WAS SO FAR INCORPORATED IN THE LOWER SIDE OF A FLEXIBLE RUBBER OR PLASTIC BOX. THE HEAD IS NOW INCORPORATED IN A DIAPHRAGM OF A DUCTILE METAL. A DIAPHRAGM WITH INCORPORATED HEAD IS MANUFACTURED BY PRESSING THE HEAD ON A POLISHED MOULD, BY THE ELECTROLESS AND/OR ELEC-   TROLYTIC DEPOSITION OF METAL ON THE SIDES OF THE HEAD AND THE ADJOINING PART OF THE MOULD, AND FINALLY BY STRIPPING THE ASSEMBLY FROM THE MOULD.

' April-30, 1914 J TGEQKEMA" "3,808,106

METHOD OF MANUFACTURING A SELF*ADJUSTI NG SUPPORTING MEMBER HAVING AMAGNETIC HEAD Original Filed Oct. 30, 1970 Fig.1

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United States Patent M US. Cl. 204-9 8 Claims ABSTRACT OF THE DISCLOSUREIn hydrodynamically operating suspension devices which have for theirobject to keep a magnetic head at a constant distance from a rotatingmemory disk, the magnetic head was so far incorporated in the lower sideof a flexible rubber or plastic box. The head is now incorporated in adiaphragm of a ductile metal. A diaphragm with incorporated head ismanufactured by pressing the head on a polished mould, by theelectroless and/ or electrolytic deposition of metal on the sides of thehead and the adjoining part of the mould, and finally by stripping theassembly from the mould.

This is a division of application Ser. No. 85,393, filed Oct. 30, 1970now Pat. No. 3,705,397.

, The invention relates to a self-adjusting supporting member having atleast one magnetic head and serving to keep said head at a constantsmall distance from a moving recording medium, a part of the saidsupporting member facing the recording medium being constructed so as tobe flexible and enclosing the part of the magnetic head in which thefront face with the operating gap is present.

Such a supporting member having a magnetic head is known from the US.patent specification No. 3,151,319 in which the part facing therecording medium is formed by the lower side of a flexible box. Said boxis manufactured from rubber or plastics, while the magnetic head may bemelted or glued in the center of the lower surface thereof.

When such a flexible box is kept at a very small distance from a rapidlymoving surface which drags along a layer of air, for example, a memorydisk, the flexible lower surface which is comparable to a diaphragmadjusts in such manner as to remain floating at a constant distance fromthe recording surface, which distance is dependent upon theinnerpressure in the box, said constant distance being maintained alsowhen-said surface comprises irregularities.

A drawback of such a supporting member which is manufactured from rubberor plastics, however, is that as a result of the specific properties ofsaid materials (plastics for example, may show recrystallization in thelong run), the location of the operative gap of the magnetic head is notaccurately defined. Actually, as a result of the plastic deformationoccurring, the magnetic head may assume a different position relative tothe recording medium. I v

It is the object of the invention to provide a device of the abovedescribed type having such a construction that the said drawback isavoided. According to the invention this is achieved in that the part ofthe supporting member facing the recording medium is a diaphragmconsistingof a 'metal provided by means of a molecular method ofproviding. a 1

It has been found possible by means of molecular meth- 3,808,100Patented Apr. 30, 1974 ods of providing to manufacture very thin metaldiaphragms (thickness from 1 to 10 microns) which have the propertiesdesirable for the above-mentioned purpose as regards ductility andrigidity.

A further drawback of supporting members of rubber or plastics is thatit is difiicult to give the lower surface a curvature which is requiredfor good floating properties, without adversely influencing thedesirable flexibility. The diaphragm according to the invention can begiven such a curvature without said drawback. It has been found that adiaphragm in the form of a dish having a flat bottom and curved edgesgives very good satisfaction.

A drawback of the known rubber or plastics supporting membersfurthermore is that the magnetic head has to be glued or melted in thelower surface. As a result of this it is substantially not possible toobtain a continuous transition between the operative surface of themagnetic head and the lower surface of the supporting member. Betweensaid surfaces a staggering of a few microns will usually occur whichadversely influences the recording properties since the distance atwhich the head must float from the recording medium is also of the orderof magnitude of a few microns.

The invention also relates to a self-adjusting supporting member havinga magnetic head which is characterized in that the front face of themagnetic head and the flexible part of the supporting member areaccurately located in one plane. This embodiment is based on theexperimentally obtained recognition of the fact that it is possible toprovidd -a thin metal film around a magnetic head by means of amolecular method of providing, for example, vapor deposition, sputteringand electroless or electrolytic deposition, without the said staggeringoccurring.

For that purpose, the method according to the invention is characterizedby the following steps: a magnetic head, or the part thereof in whichthe front face is present, is pressed on a very smoothly polished mouldof the desirable shape with the front face of the magnetic head facingthe mould.

Although the method according to the invention permits of providing afilm of metal around a magnetic head without staggering so that a trulyplane floating surface is obtained, the invention, presents thealternative possibility of providing, on purpose, an offset which can beaccurately determined by means of the mould. This means that a diaphragmcan be manufactured from which the head projects over a distance whichcan be accurately determined, while in addition the requirement can befulfilled that the front face of the head be parallel to the frame ofthe diaphragm.

According to a preferred embodiment of the method according to theinvention such a construction can be realized by etching away a part ofthe surface of the mould down to a depth which corresponds to thedistance over which the head is to project, and by arranging the head,or the part thereof which comprises the operativegap, in the etched-awaypart. The diaphragm can then be provided in the above-described manner.

An advantage of the construction thus obtained is that, for example'bymeans of a diaphragm from which a head projects by '4 microns, thediaphragm can be made to float at a distance of 6 microns from the disk,so that the effective floating distance of the operative face of thehead is only 2 microns. The difficulties associated with the floating of'a diaphram at distances of 2 microns (and less) from a memory disk arehence avoided.

An advantage of the method described is in particular that, since themould can be used over and over again, heads which project accuratelyequally far from a diaphragm can be mass-produced.

A thin layer of metal is provided on at least a part of the sides of themagnetic head and the surface of the mould by means of a molecularmethod of providing the metal film with magnetic head is chemically ormechanically (stripping) removed from the mould.

A good adherence of the metal film to the magnetic head is of greatimportance. For a good adherence the film should readily adjoin thesides of the magnetic head, in other words, the corners formed by thesides of the head and the bottom of the mould should be readily filled.

It has been found that metal deposited from an electroless bath providesa readily adhering layer which extends continuously in corners andreadily follows the corners.

A preferred embodiment of the method according to the invention istherefore characterized in that the metal is deposited from anelectroless bath on at least a part of the sides of the magnetic headand on at least the adjoining part of the surface of the mould.

A further preferred embodiment of the method according to the inventionis characterized in that a first metal is deposited from an electrolessbath on at least a part of the sides of the magnetic head and on theadjoining part of the surface of the mould, after which the metal filmis completed by electrolytically depositing a second metal until thedesirable thickness is obtained.

The advantage of an electrolytically deposited metal layer for which Cuhas been found to be very suitable is that the deposition occurs morerapidly than with the electroless method, while in addition a strongermetal layer can be obtained.

The process of the electroless deposition of the desirable metal ispreferably started on an activated layer.

Good results are obtained in particular with the electroless depositionof NiP on a layer of Ni or Pd provided previously in an electrolyticbath.

A preferred embodiment of the method according to the invention ischaracterized in that NiP is used for the metal to be provided from theelectroless bath, that cu is used for the metal to be providedelectrolytically and that a layer of Pd is provided electrolytically asan activated layer.

In order that the invention may be readily carried into effect, it willnow be described in greater detail, by way of example, with reference tothe accompanying drawing, in which FIG. 1 shows an embodiment of themethod according to the invention,

FIG. 2 is a cross-sectional view of a suspension device according to theinvention.

FIG. 1 shows how a metal diaphragm is manufactured by means of themethod according to the invention and which forms one rigid assemblywith a magnetichead, while the transition from the active surface of themagnetic head to the diaphragm shows no staggering.

Reference numeral 1 denotes a mould which has a very smoothly polishedinner surface and which has a curvature desirable for the diaphragm tobe manufactured. Dependent upon the way in which the metal for thediaphragm is provided, the material of the mould may be metallic (forexample, stainless steel) or non-metallic (for example, glass). Sincethe diaphragm has to be removed from the mould after its manufacture, itis recommendable to take measures beforehand to facilitate said removal.When the mould consists of glass, it should previously be slightlyroughened, for example, in such manner that during the deposition themetal readily adheres and forms no blisters, whilenevertheless it caneasily be stripped from the substrate after it has been deposited.Another manner is first to provide a separation layer 2 on the mould orto use a mould which by nature alreadyhas a separation layer (forexample, an oxide layer). It is to be noted that in particular adeposited layer of copper can easily be removed from a stainless steelmould.

A magnetic head 4, or if desirable only the operative gap including partthereof, is then laid-on the mould with the operative surface 3 and keptpressed against it. In the case in which the magnetic head consists offerrite, first an electrically readily conducting layer is provided onthe ferrite, for example, of Au. It is recommendable to provide saidlayer on a layer of a metal which readily adheres to ferrite, forexample Cr.

After these preparatory measures, the metal layer 6 is provided. A metalwhich as regards mechanical properties is suitable for this purpose isCu. The mould 1 with the head 4 rigidly pressed thereon is for thatpurpose immersed in a copper bath. This may be both an electroless bath,that is to say a bath from which a metal layer is depositedhomogeneously and with a uniform thickness on an activated layer, byelectroless plating and an electrolytic bath. From electrodepositiontechnology are known, for example, a series of electrolytic Cu-baths, inwhich there may be distinguished between baths having a goodmicrospreading (i.e. the smallest irregularities are filled), bathshaving a good microspreading (i.e. a layer having a homogeneousthickness is obtained without particular requirements being imposed uponthe arrangement of the electrodes), or baths which combine bothproperties to a greater or smaller extent. In the embodiment describedhere, an electrolytic Cu bath is used which ensures particularly a goodmicro-spreading. Composition: copper sulphate 200 g., concentratedsulphuric acid 55 g.; hydro.- chloric acid 25 mg; glaze 3 ml.

It is recommendable to secure one of the electrodes exactly opposite tothe head on the outside 11 of the mould.

In the proximity of the head the metal is then deposited as uniformly aspossible. It is possible to place the other electrode or electrodes insuch manner that a flexible film is obtained around the head in athickness of 5 to 6 microns and to cause the thickness of the layer toincrease beyond the said region so that a non-deformable and readilyhandable edge is obtained.

Since it has been found that an electroless-deposited metal in cornersgives a continuously extending and hence readily adhering connection, alayer of electroless metal 5 is provided on the sides of the head and onthe adjoining part of the bottom of the mould prior to the electrolyticdeposition of the layer 6. In the example described, said metal 5 is alayer of NiP, thickness a few microns. In order to start the depositionhereof, first a layer of Pd (2) of from 300 to 500 A. iselectrolytically deposited on the mould.

After the layer 6 has finally been provided the diaphragm thus obtainedis removed from the base. The separation layer 2 may partly remain onthe mould but the thickness hereof is so small, in the example describedless than 0.05 micron, that the staggering between the active surface ofthe head and the diaphragm is negligible. In order to avoid that theextremely thin diaphragm creases during the removal from the base, it ispossible, for example, to provide on the base previously a thicker layer(for example, from 10 to 20 microns) of another metal. This layer isafterwards removed together with the diaphragm, after which thediaphragm alone is obtained by chemically dissolving the supportinglayer.

FIG. 2 shows how a diaphragm 6 with incorporated head 4 manufacturedaccording to the method described is secured (for example, by clampingor soldering) in a. holder 10 and together with an upper part 7 forms aclosed space 8. This device is positioned at a very small distance froma recording medium 9 (which may be, for example a memory disk) which,during operation, moves in the direction of the arrow at a high speedrelative to the suspension device. The diagram then adjusts so that itremains floating at a constant speed h from the disk 9 This distance hmay be a few microns. So the diaphragm will adapt to irregularities ofthe surface of the recording mediumso that the danger of damage to themagnetic head is very small. It is to be noted that the distance h canbe controlled by giving the space 8 a different pre-pressure.

As already noted above, another aspect of the invention is thepossibility of causing a head to project over an accurately determineddistance from the diaphragm so that problems associated with thefloating of a diaphragm at a very small distance from a memory disk canbe avoided.

Another important aspect is that a number of magnetic heads, whether ornot cohering together, or only the operative gap including parts thereofcan be incorporated in a simple manner in one diaphragm whilemaintaining the uniformity of the floating surface.

What is claimed is:

1. A method of manufacturing a magnetic head assembly comprising amagnetic head and a self-adjusting flexible diaphragm member of givenshape for said head, said head being supported on one side of saiddiaphragm and having active pole shoe portions thereof accessible fromthe other side of said diaphragm, said method comprising the steps:

(A) positioning said magnetic head on a smoothly polished mold having ashape compatible with the said given shape of said diaphragm with thesaid active pole shoe portions in confronting relationship to thesurface of said mold and at a portion of the surface of said moldcorresponding to the position of said head in said diaphragm,

(B) molecularly depositing a thin metal layer on the exposed portion ofsaid mold and on the side portions of said magnetic head, said layerhaving a thickness sufficient to form a self sustaining unit assembly ofsaid layer and said magnetic head, and

(C) detaching the said layer and said magnetic head as a unit assemblyfrom the said mold.

2. A method as claimed in claim 1 wherein said mold is provided with anetched recess at the portion thereof corresponding to the desiredposition of said active pole shoe portions, and said magnetic head ispositioned with the active pole shoe'portions thereof in said recessprior to the deposition of said thin layer of metal.

3. A method as claimed in claim 1 wherein the deposition of said thinmetal layer comprises the steps of electroless depositing a first layerof a first metal on the exposed surfaces of said mold and the sides ofthe magnetic head and thereafter electrolytically depositing a secondmetal layer on said first layer.

4. A method as claimed in claim 3 comprising the step of depositing anactivating metal layer on the sides of said magnetic head prior to thedeposition of said thin metal layer.

5. A method as claimed in claim 4 wherein the step of depositing anactivating metal layer on the sides of said magnetic head comprises thestep of forming a chromium deposit on said sides and superimposingthereon a layer of gold.

6. A method as claimed in claim 1 further comprising the step ofapplying a separation layer on said surface of said mold prior topositioning said pole shoe portions thereon.

7. A method as claimed in claim 1 further comprising the steps ofinitially forming on said mold surface a layer of a materialdifferentially soluble with respect to the material of said depositedthin metal layer, separating said initial layer and said thin metallayer and magnetic head as an integral assembly from the mold surface,and differentially dissolving said initial layer from the so separatedassembly.

8. A method as claimed in claim 4 wherein the metal of said activatinglayer is Pd wherein the metal of the electroless deposition is NiP andwherein the metal of the electrolytic deposition is Cu.

References Cited UNITED STATES PATENTS 3,488,648 1/1970 Church 340-1741E 3,187,639 6/1965 Kelly et al. 204-9 3,091,578 5/1963 Hetherington204-l6 1,394,085 10/1921 Halvorson 204-7 THOMAS M. TUFARIELLO, PrimaryExaminer U.S. Cl. X.R.

